Integration of light and circadian signals that regulate chloroplast transcription by a nuclear‐encoded sigma factor

Belbin, Fiona E.; Noordally, Zeenat; Wetherill, Sarah J.; Atkins, Kelly A.; Franklin, Keara A.; Dodd, Antony N.

doi:10.1111/nph.14176

“…Although cryptochromes contribute to both blue-and green-light signalling pathways into the circadian system (Figures 3, 4, and 5 (Belbin et al, 2016) but differ from earlier reports that included sucrose as a media additive . By contrast, loss of cryptochrome function under green light causes an extension of circadian period without an associated loss of amplitude that is masked by the addition of supplemental sucrose (Figures 3, 4, 5, and S6b).…”

Section: Cryptochrome Signalling Into the Circadian System Is Disticontrasting

confidence: 75%

Cryptochromes integrate green light signals into the circadian system

Battle

¹

,

Jones

²

2019

Plant Cell & Environment

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Plants are acutely sensitive of their light environment, adapting their growth habit and prioritizing developmental decisions to maximize fecundity. In addition to providing an energy source and directional information, light quality also contributes to entrainment of the circadian system, an endogenous timing mechanism that integrates endogenous and environmental signalling cues to promote growth. Whereas plants' perception of red and blue portions of the spectrum are well defined, green light sensitivity remains enigmatic. In this study, we show that low fluence rates of green light are sufficient to entrain and maintain circadian rhythms in Arabidopsis and that cryptochromes contribute to this response. Importantly, green light responses are distinguishable from low blue light‐induced phenotypes. These data suggest a distinct signalling mechanism enables entrainment of the circadian system in green light‐enriched environments, such as those found in undergrowth and in densely planted monoculture.

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“…This circadian effect on the intensity and dynamics of a response to environmental change is a signature of circadian gating ( Hotta et al, 2007 ; Greenham and McClung, 2015 ). Though circadian gating has been observed (e.g., [ Belbin et al, 2017 ]) and modeled without any knowledge of the transcriptional regulation ( Dalchau et al, 2010 ) in plants, it remains unclear what gene regulatory circuits are sufficient to explain such behavior.…”

Section: Resultsmentioning

confidence: 99%

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

Piechura

¹

,

Amarnath

²

,

O’Shea

³

2017

eLife

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The circadian clock interacts with other regulatory pathways to tune physiology to predictable daily changes and unexpected environmental fluctuations. However, the complexity of circadian clocks in higher organisms has prevented a clear understanding of how natural environmental conditions affect circadian clocks and their physiological outputs. Here, we dissect the interaction between circadian regulation and responses to fluctuating light in the cyanobacterium Synechococcus elongatus. We demonstrate that natural changes in light intensity substantially affect the expression of hundreds of circadian-clock-controlled genes, many of which are involved in key steps of metabolism. These changes in expression arise from circadian and light-responsive control of RNA polymerase recruitment to promoters by a network of transcription factors including RpaA and RpaB. Using phenomenological modeling constrained by our data, we reveal simple principles that underlie the small number of stereotyped responses of dusk circadian genes to changes in light.

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“…This circadian effect on the intensity and dynamics of a response to environmental change is a signature of circadian gating [4,5]. Though circadian gating has been observed (e.g., [35]) and modeled without any knowledge of the transcrip-tional regulation [36] in plants, it remains unclear what gene regulatory circuits are sufficient to explain such behavior.…”

Section: Regulation Of Dusk Gene Expression By Rpaamentioning

confidence: 99%

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

Piechura

¹

,

Amarnath

²

,

O’Shea

³

2017

Preprint

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The circadian clock interacts with other regulatory pathways to tune physiology to predictable daily changes and unexpected environmental fluctuations. However, the complexity of circadian clocks in higher organisms has prevented a clear understanding of how natural environmental conditions affect circadian clocks and their physiological outputs. Here, we dissect the interaction between circadian regulation and responses to fluctuating light in the cyanobacterium Synechococcus elongatus. We demonstrate that natural changes in light intensity substantially affect the expression of hundreds of circadian-clock-controlled genes, many of which are involved in key steps in metabolism. These changes in expression arise from control of RNA polymerase recruitment to promoters by circadian and light-responsive regulation of a network of transcription factors including RpaA and RpaB. Using phenomenological modeling constrained by our data, we reveal simple principles that underlie the small number of stereotyped responses of dusk circadian genes to changes in light.Circadian clocks allow organisms from almost all branches of life to alter physiology in anticipation of diurnal changes in the environment. Circadian clocks keep time using autonomous core oscillators which control output pathways to direct periodic changes in the mRNA levels (expression) of genes, ultimately leading to oscillations in higher order behaviors [1]. Laboratory studies of the outputs of circadian clocks have been primarily performed under constant conditions to isolate circadian regulation from environmental responses. In nature, however, organisms with circadian clocks must also cope with unexpected fluctuations in the environment. Thus a major challenge in chronobiology is to understand circadian clocks and their outputs in dynamic environments.Previous studies suggest that circadian clock output pathways interact with environmental responses to tailor physiological outputs to both the time of day and the current state of the environment. For example, sleep/wake cycles in Drosophila melanogaster and photosynthesis in Arabidopsis thaliana are controlled by both the circadian clock and environmental variables like day length or light [2,3]. Further, circadian clocks can modulate environmental responses based on the time-of-day in a process called circadian gating [4,5]. However, the complexity of higher organisms has prevented a detailed understanding of the interaction between circadian timing information and environmental responses. In contrast, the circadian clock in the cyanobacterium Synechococcus elongatus PCC7942, an obligate photoautotroph, has a simple architecture which controls gene expression oscillations ( Figure 1A) to influence metabolism and growth. S. elongatus must carefully monitor its environment, as the sunlight required for photosynthesis fluctuates on the * These authors contributed equally to this work.† Correspondence: osheae@hhmi.org minute, day, and seasonal timescales (Figure 1B,[6]). While it is well understood how the ...

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Integration of light and circadian signals that regulate chloroplast transcription by a nuclear‐encoded sigma factor

Cited by 43 publications

References 75 publications

Cryptochromes integrate green light signals into the circadian system

Cryptochromes integrate green light signals into the circadian system

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

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